Plastic closure comprising a cutting and perforating device

ABSTRACT

The invention relates to a closing device ( 1 ) consisting of a plastic material for applying to a closed container consisting of a plastic film material. Only two cutting teeth ( 20, 21 ) of the same height are to be applied to the cylindrical perforator ( 5 ) of said device, said teeth being arranged in an angular region of between 70° and 120° of the circumference. In this way, the section of the subsequent tooth extends into the section of the previous tooth, enabling a secure opening, without the risk of cutting an entire rondelle out of the plastic film of the container. The creation of only two partial sections without producing an opening in the container is also prevented.

BACKGROUND OF THE INVENTION

The present invention relates to a closing device consisting of aplastic material for applying to a closed container consisting of aplastic film material, wherein said closing device comprises a lowerpart with a cylindrical outlet and a flange for attaching same to thecontainer and a screw cap which is screwably fixed to the lower part.Said closing device further comprises a cylindrical perforator havingexternal thread, which is open to both sides in the axial direction andtravels in the outlet of the lower part, in the internal thread thereof,wherein means are located in the screw cap, which move the perforatordownwards in a helical manner during the initial unscrewing movement ofsaid screw cap and wherein said cylindrical perforator has cutting teethon the cylindrical wall thereof at the end which is directed towards thecontainer wall.

Closing devices of the type previously mentioned have to date only beenapplied to containers produced from laminated film material. Theselaminated films comprise at least three layers of different types ofmaterial. First of all, such a film consists of a cardboard layer, whichprovides the container with the necessary rigidity, an aluminum layerserving as an aroma barrier and a plastic layer which ensures therequired denseness. In order to separate these three layers, thecorresponding perforator of the aforementioned closing device mustfulfill various functions. A plurality of saw teeth are oftenrecommended for separating the cardboard layer, wherein a raised toothcuts through the aluminum layer with a forward cutting edge and whereina perforating tooth breaks through the plastic layer before theaforementioned cutting edge can continue to cut the plastic film. In thecase of these containers consisting of laminated film material, theseparation of the cardboard material generally represents a problem.Particularly if the partial press cut, which serves as a support and atleast separates the cardboard layer to some extent, does not exactlycorrespond to the cutting line of the perforator, the teeth are theneither too weak or in the case of a considerable number of teeth, thecardboard material comes between the teeth and said teeth can thereafterhardly produce a perforating effect.

SUMMARY OF THE INVENTION

The present invention relates, however, to a closing device, which isapplied to a pure plastic film material. Such tubular receptacles,mostly referred to as pouches in the technical language, have not beenopened to date by means of the aforementioned closing devices. On thecontrary, an opening was already punched out and a closure including theoutlet thereof was welded on the pouches so as to be correctlypositioned or was shrink-wrapped between two film layers. Because theshelf-life of the filled food material or beverage is thereby solelydependent upon the impermeability of the closure, such closures werevirtually used only in unproblematic areas, particularly in the area ofcosmetics.

When using a closing device of the kind mentioned at the beginning ofthe application, the container pouch remains completely closed until thepoint of first being opened. An increased shelf-life is therebyprovided. In addition, the plastic film in such applications accordingto the invention is substantially more robust and is designed having agreater wall thickness than the very thin plastic film layer in the caseof a laminated film. This in turn gives rise to other demands beingplaced on the closing device. Initial trials with closing devices fromprior art did not produce any reliable results.

Perforators as, for example, from the American patent publications U.S.Pat. No. 5,020,690 or U.S. Pat. No. 5,141,133 comprise a plurality ofteeth. These teeth abutting one another basically form the shape of anannular saw blade. Such solutions have either led to a rondelle beingcompletely cut out of the plastic film and falling into the container oras a result of the toughness of the film to individual teeth beingbroken off and falling into the container. Because the containersinvolved here typically relate to containers for beverages, this istotally unacceptable.

It has been assumed up until now that a plurality of teeth isadvantageous because a plurality of perforations thereby arise. It has,however, actually been determined that a plurality of perforations donot provide an advantage per se. It has in fact been shown, that aplurality of teeth automatically leads to these teeth having to berelatively weak. This leads to the disadvantage previously mentionedabove.

Based on this realization, further developments have accordingly beenput into place, in which on the one hand the number of teeth was reducedand on the other hand the shape of the teeth was variably configured. Asolution is therefore known, for example, from the European patentpublication EP-A-1415926 having equally high teeth, which, however, aredistributed over the periphery in a non-uniform manner. In addition, aclosing device of the type mentioned at the beginning of the applicationis known from the American patent publication U.S. Pat. No. 6,279,779having a perforator which comprises only a single tooth. This tooth isdesigned in a suitably strong manner and has different surfaces with adifferent effect. The one-tooth version has definitely not proven itsworth. The procedures for severing the film as well as the perforationthereof, the subsequent cutting of the complete material and finally thefolding away of the cut-out part have not been able to be optimized in asingle element. The applicant therefore conducted trials with aperforator according to the WIPO patent publication WO2007/030965,wherein three teeth are present, which are distributed over theperiphery and are minimally offset from a uniform distribution. Eventhough perforators of this type have proven their worth in manyinstances, cases frequently occur in which either the film is completelycut out and the corresponding rondelle fell into the receptacle or inother cases the films were cut only at three locations to anapproximately equal width and the film remained hanging in an occludingmanner over the opening. Based on these realizations, the applicantundertook elaborate trials to find an optimal solution, which reliablyimplements an opening incision in such a way that a flap-like rondelle,which stays in contact with the receptacle, remains hanging, saidrondelle also being pushed out of the open area of the perforator by theteeth.

A closing device of the kind mentioned at the beginning of theapplication meets this aim, wherein said device is characterized byhaving exactly two equally high teeth which are arranged in an angularregion of between 70° and 120° of the circumference. This has the effectthat the plastic film to be cut open is pre-tightened by the two teethand that said teeth subsequently begin to perforate and cut the film.After a short distance, the subsequent tooth then extends into thecutting area of the previous tooth and is thereby rendered inoperative.If the perforation of the film occurs virtually immediately upon firstcontact, the film still cannot completely be annularly cut out andconsequently a plastic film rondelle does not fall into the container.If the perforation and the following incision occur relatively late, asufficiently long incision is still produced, which ensures that thesection of the subsequent tooth runs into the area of the section of theprevious tooth and as a result a section is still achieved, whichextends more than 180°; thus enabling the film to be cut opensufficiently wide to achieve a sufficient flow rate.

As previously mentioned, the closing device according to the inventionis applied to a container consisting of a pure plastic film material.This one or multiple layer plastic film is substantially thicker thanthe plastic film which is used as an impermeability layer in thecomposite film consisting of diverse materials.

Whereas in the case of the thin film, wherein the perforation mustforemost be done to ensure a reliable opening on account of the highelasticity of said film, this appears to no longer play a central rolein the case of the film now being used. Experiments observed at a strongmagnification have shown that apparently the film is slit open whileforming swarf.

In light of this evidence, it is therefore an additional aim of thepresent invention to equip the teeth with swarf control means as in thecase of a steel processing cutting plate. In solutions from prior art,this swarf has actually accumulated on the tooth tip and the torqueoutput applied by means of said prior art was thus substantially higherthan is the case with the now present solution.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred exemplary embodiment of the subject matter of the inventionis depicted in the drawings and subsequently described. In the drawings:

FIG. 1 shows the closed plastic closure prior to initial use in a sideview and

FIG. 2 shows the same in a diametral vertical section

FIG. 3 shows in a simplified depiction the perforator from below with aview of the edge having the two cutting teeth

FIG. 4 shows the perforator and the lower part with a flange as aone-piece subassembly prior to assembly, again in a diametral verticalsection and

FIG. 5 the same view rotated 180°.

FIG. 6 a-6 c show various sectional views.

FIG. 7 shows a perforator suitable for harder plastic films comprisingtwo teeth which are offset at an angle and have different cuttingcharacteristics and

FIG. 8 shows the same perforator rotated 120°.

FIG. 9 shows a load-time diagram for the perforator according to theFIGS. 7 and 8, whereas

FIG. 10 shows such a load-time diagram for the perforator having thetooth configuration according to the FIGS. 4 and 5.

DETAILED DESCRIPTION

The plastic closing device is denoted in its entirety with the numeral1. Said device comprises three components, of which two can be producedas one piece resulting from the manufacturing processes thereof, as issubsequently described in FIGS. 4 and 5. Said plastic closing device 1comprises a screw cap 4, on the lower edge of which a tamper evidenceband 7 is molded via predetermined breaking point bridges so as to alignwith the jacket wall of the screw cap. In the side view according toFIG. 1, only a flange 3, which is a part of the lower part 2, of theclosing device 1 can be seen.

In the cross-sectional view according to FIG. 2, it can be seen that thescrew cap 4 has a jacket wall 9 as well as a top surface 10. Said screwcap 4 has internal screw thread 11 which is designed as fine-pitch-pitchthread. The lower part 2 including the flange 3 thereof, which serves asa welded or glued connection to the container, comprises a cylindricaloutlet 6, which is tubular and open to both sides. This outlet 6 hasexternal thread 12 which is also designed as fine-pitch thread andmeshes with the internal thread 11 of said screw cap 4 when said screwcap 4 is screwed on and off. The fine-pitch thread 11, 12 is preferablydesigned as a double-start thread. The fine-pitch thread has theadvantage of easy assembly due to the internal thread of the said screwcap being able to be pushed over the external thread 12 of the outlet 6in a ratchet-like manner. This allows for assembly without a relativerotation of the parts with respect to one another. Two driving elements13 diametrically opposed to one another are located in said screw cap 4,wherein said driving elements are integrally formed with the bottom sideof the top surface 10 of said screw cap 4. Said driving elements 13 acttogether with the driving element 14 in the perforator 5. Saidperforator 5 is subsequently described in detail with the aid of FIGS. 4and 5.

As previously described, the perforator 5 and the lower part 2 aremanufactured as one piece, just as is depicted in FIG. 4. In this case,said lower part 2 and said perforator 5 together form a subassembly,which can be manufactured using a single injection mold. Duringassembly, said lower part 2 and said perforator 5 can simply be pushedtogether. In so doing, said perforator 5 comes to rest completely withinthe cylindrical outlet 6. In this position, said perforator 5 isintegrally formed as a subassembly on the upper edge of the outlet 6 viapredetermined breaking points. Said perforator 5 consists of acylindrical pipe section 16, which has course thread 17 on the outside.Said course thread 17 having a large pitch meshes with a correspondinglyadapted trapezoidal thread 18 on the inside of the outlet 6. Saidperforator 5 additionally comprises two entraining ribs 19 which arediametrically opposed to one another and on which the aforementioneddriving elements 13 of the screw cap 4 make contact during therespective screwing movement. Two cutting teeth are integrally formed onthe lower edge of said perforator 5. Both of said teeth can be seen inFIG. 2, whereas in FIG. 5 only the subsequent tooth can be seen whilethe leading tooth has been cut away. Said leading tooth is denoted withthe reference numeral 20 and said subsequent tooth with the referencenumeral 21. Both teeth 20, 21 have the same length l. This lengthdesignates the vertical distance from the lower edge 22 of thecylindrical pipe section 16 to the tip of the corresponding cuttingtooth.

In the assembled state as is shown in FIG. 2, the perforator 5completely lies within the cylindrical outlet 6. The tip or rather thetwo tips of the cutting teeth 20, 21 lies at the height of the loweredge of the flange 3 of the lower part 2. When the screw cap 4 isunscrewed, said perforator 5 moves axially in the opposite direction,wherein said perforator carries out a substantially larger translationalvertical travel per rotation than said screw cap 4 in the oppositedirection. Said perforator 5 actually carries out maximally a rotarymotion of around approximately 330°, whereas said screw cap goes throughone or several turns until being completely unscrewed.

Depending upon strength, elasticity and other factors, in particularwith regard to the pre-tightening force on the plastic film of the pouchreceptacle, the plastic film is sooner or later perforated. Said film ispractically always perforated simultaneously by the cutting teeth 20,21. The sectional views as depicted in FIGS. 6 a to c thus arise. InFIG. 6 a, the partial sections of the subsequent tooth have not yetadvanced into the section of the leading (previous) tooth. On the otherhand in FIG. 6B, this has already happened. This figure shows thecutting line obtained in the worst case, which lies in the magnitude of200 to 240°. Were this the end position, the leading (previous) toothwould basically push the flap-like part L downwards so that also in thiscase, the passage is open more than 50%. The cutting line normallyextends about a partial circle of around 330°. This situation isdepicted in FIG. 6 c.

In FIG. 3, the perforator 5 is depicted in a simplified form with a viewof the teeth in the direction of the rotational axis of the cylindricalpipe section 16. If radii are drawn from tooth tips to the center of thelongitudinal axis, an angle α is then formed between them. Said angle αmust be within an angular range between 70° and 120°. In addition, it isadvantageous if the steepness of the external thread of the perforator 5and the internal thread 18 of the outlet 6 are selected in such a waythat during the unscrewing movement of the screw cap 4, the cuttingteeth 20, 21 travel through a maximum cutting distance of 210° in thecutting direction from the point of contact on the plastic film of thecontainer to be severed up until said unscrewing movement of said screwcap 4 has completely ended. If the maximum angle, which the leadingtooth 20 and the subsequent cutting tooth 21 enclose together, namely anangle of 120°, is now added to the 210°, this then results in a maximumcutting line which extends over 330°. A sufficient connection betweenthe plastic film of the container and the aforementioned flap L therebyremains. If the worst case is assumed, that the perforation of the filmfirst occurs after a quarter turn, i.e. after 90°, and the angle betweenthe two cutting teeth amounts to only 70°, said leading tooth stillimplements a minimum cutting line of 120° while said subsequent tooth 21travels through the additional 70°; thus enabling a cutting line of over180° also to be formed in the worst case.

Because the resulting forces on the cutting teeth are substantiallygreater in this version than in the case of a plurality of small teeth,it is advantageous for the wall thickness of the cutting teeth 20, 21 tobe selected to be larger than the wall thickness of the cylindrical pipesection 16 of the perforator. This can be seen most clearly in FIG. 5.This does not appear to be the case in FIG. 4; however, this is merelydue to the fact that the cutting line travels in this instance throughthe entraining ribs 19.

It is known that plastic films can be obtained in many differentqualities. Said films differ not only in the selection of the plasticmaterials used but also in thickness, stiffness, hardness, etc. Withregard to the production of pouch receptacles, which are to have acomparable strength to those consisting of multilayered laminatescomprising cardboard, such plastic films cannot be reliably opened withthe plastic closing devices known to date. The stronger the film beingused was, the greater the thickness of the teeth had to be, and in doingso the films could hardly be opened without too high of a torque beingrequired for the operation, which then users could not be expected toproduce. The pouch receptacles were in fact entirely manufactured fromthis relatively thick and hard material, wherein, however, an openingwas press cut and sealed with a film section, which was substantiallysofter and could be cut with the usual plastic closing devices knownuntil that time. The plastic closing device was in turn welded to thefilm section.

The trend is to move away from this technology and it has been shownthat this is possible if the leading as well as the subsequent tooth isdesigned in the manner depicted in FIGS. 7 and 8. Whereas emphasis wasespecially placed on a perforation of the film when using the teeth fromprior art, weight is now placed on the cutting of the film. In the caseof the softer plastic films, a much stronger stretching occurs andaccordingly it was essential for the two teeth to make contact atapproximately the same time and thereby to tighten the film so that aperforation takes place. After that, the film itself could subsequentlybe cut practically without resistance along the cutting edge of thecorresponding teeth. This process is, for example, depicted in thetime-load diagram according to FIG. 10. FIG. 9, on the other hand, showsthe load-time diagram of the perforator according to FIGS. 7 and 8comprising the new tooth configuration. Both curves cannot be directlycompared when considering the fact that a thin, substantially moreelastic film is cut in the case depicted in FIG. 10 whereas a thickerfilm, which is substantially harder but less elastic, has been cut inthe diagram according to FIG. 9.

It can be seen in FIG. 10 that the torque increases more slowly up untilthe point in time of the perforation by a first of the two teeth,whereupon the torque immediately drops until the second tooth begins tohave an effect and then subsequently falls very sharply.

In contrast thereto, when severing the thicker film using the perforatorcomprising the newly designed teeth shapes, the load which has to beapplied increases faster until the maximum pressure occurs on the filmand the cutting action begins. The load now continuously decreases untilthe first succeeding tooth begins to have an effect and the additionaleffect of the further succeeding teeth can then additionally be seen inthe region where the drop in load occurs. Despite the substantiallyharder film, the required force output remains practically the same.This astonishing result is due to the fact that the thicker film hardlyever tears but has accordingly to be cut much more, wherein the cuttingcharacteristics resemble a cutting plate of a lathe tool. It can bemicroscopically determined that swarf forms at the same time the plasticis cut, and this swarf must be able to be routed into an area away fromthe teeth in order to prevent said swarf from moving in front of theactual cutting point of the teeth and thereby substantially increasingthe torque.

A preferred exemplary embodiment of these newly configured teeth of aperforator is explained below with the aid of FIGS. 7 and 8. Theperforator in its entirety is denoted with the reference numeral 5. Thistoo comprises a cylindrical pipe section 16, on the outside of which acoarse thread 17 is molded. The trapezoidal thread 18 then engages insaid coarse thread 17 in the cylindrical outlet 6. The cylindricalsection 16 is equipped on the inside with entraining ribs 19. In thisoption, the cylindrical section 16 is reduced in diameter in the lowercutting region 26 by approximately the depth of said coarse thread 17.Provision is made in turn at the lower edge of this tapered cuttingregion 26 for a leading cutting tooth 20 and a subsequent cutting tooth21. Whereas in the previously described option of this cutting tooth, astraight, relatively steep cutting surface is present in the leadingposition in the cutting direction, this leading cutting edge is in thiscase tiered; and there is a plurality of succeeding teeth 24, which aretiered at different heights, arranged in a staggered manner. Dependingupon the penetration depth, said succeeding teeth 24 are employed oneafter the other A swarf receiving space 25, which runs approximatelyarcuately, is situated between in each case the foremost leading andsubsequent cutting tooth 20, 21 and the cutting tooth 24 disposed in theleading position in the cutting direction. Such a swarf receiving space25 is also in each case situated between two succeeding teeth 24arranged adjacently in each case. This can be seen most clearly in FIG.7.

In contrast to the solution first shown, wherein the teeth performpractically only a perforating action by means of a perforating tip 23and thereafter the leading cutting edge 28 comes into operation, the twomain teeth, namely the leading cutting tooth 20 and the subsequentcutting tooth 21, as well as the staggered succeeding teeth 24 all workin this case the same and have altogether a swarf-removing cuttingeffect. After the leading tooth and the subsequent tooth 20, 21 havecome through the film, a succeeding tooth 24 must therefore take ontheir function. Said succeeding teeth are therefore disposed accordingto height in a descending step-like succession on account of theperforator 5 penetrating ever deeper into the container to be cut openduring the screwing action. Said succeeding teeth also operate in aswarf-removing manner and thus said succeeding teeth are also equippedin each case with a respective swarf receiving space 25. It isappropriate for the swarf receiving spaces 25 which operate first to belarger that the swarf receiving spaces that subsequently becomeoperative.

1. A closing device (1) made of a plastic material for applying to aclosed container made of a plastic film material, wherein said closingdevice comprises a lower part (2) having a cylindrical outlet (6) and aflange (3) for attaching to the container and a screw cap (4) which isscrewably fixed to the lower part (2) as well as a cylindricalperforator (5) having an external thread, which is open on both sides inan axial direction and travels in an internal thread in the outlet (6)of said lower part (2), wherein means (44) are located in the screw cap(4) which during initial unscrewing movement of said screw cap (4) movethe perforator (5) downwards in a helical manner and wherein saidcylindrical perforator (5) has cutting teeth on a cylindrical wallthereof at the end which when mounted is directed towards the containerwall, characterized in that said perforator has exactly two cuttingteeth of the same height, both of which are arranged in an angularregion of between 70° and 120° of a circumference.
 2. The closing deviceaccording to claim 1, characterized in that a wall thickness of the twocutting teeth is thicker than a wall thickness of a cylindrical jacketwall of the perforator.
 3. The closing device according to claim 1,characterized in that a steepness of the external thread (12) of theperforator (5) and the internal thread (18) of the outlet (6) isselected in such a way that during the unscrewing movement of the screwcap (4), a tooth moving in a cutting direction travels through a maximumcutting distance of 210° from a point of contact on the plastic film ofthe container up to a point where the unscrewing movement of said screwcap has completely ended.
 4. The closing device according to claim 1,characterized in that the external thread of the outlet is adouble-start fine-pitch thread.
 5. The closing device according to claim1, characterized in that the external thread of the perforator and theinternal thread of the outlet have a trapezoidal thread profile.
 6. Theclosing device according to claim 1, characterized in that at least oneof the two cutting teeth (20, 21) has a number of staggered succeedingteeth (24), which are arranged at different heights in a descendingstep-like succession, so that depending upon a penetration depth of theperforator into the film to be cut, one succeeding tooth after the otheris operative and wherein a swarf receiving space (25) is located in eachcase between the respective foremost cutting tooth (20, 21) and the nextoperative succeeding tooth as well as between two adjacent succeedingteeth.
 7. The closing device according to claim 6, characterized in thatthe swarf receiving spaces (25), which are operative at first, arelarger than the swarf receiving spaces which are subsequently operative.